The present invention relates to machines for the handling of rod-like articles such as for example cigarettes and filter plugs. More particularly, the invention relates to cigarette-making machines, in which a continuous cigarette rod is cut into single segments presenting the length of a cigarette or a multiple of this length.
After the segments (cigarettes) after they been cut from the cigarette rod, they are accomodated singularly inside the successive flutes of a rotary transfer drum, in order to be subsequently sent to further processing stations.
In the rotary transfer drums, the flutes present at their bottom a row of suction ports or orifices, which are put in communication with a source of pneumatic vacuum. Thus, the desired suction effect is obtained, for holding the cigarettes firmly in the flutes, and for gently braking their inlet speed into the flutes (the cigarettes are fed at a relatively high speed, lengthwise, into the suction flutes of the transfer drum), so that the cigarettes abut gently, with no shocks or bouncing, against an abutment member provided at the end of the flute opposite to the inlet end.
Now, it appears evident that the inlet speed of the cigarettes running lengthwise into the flutes increases proportionally with the speed of production, or working speed, of the cigarette-making machine.
Consequently, in order to obtain and maintain an optimum braking effect due to the suction, at each value of the inlet speed of the cigarettes into the flutes (which speed is proportional to the speed of production of the cigarette-making machine), there should correspond a determined value of the vacuum which generates the suction effect through the ports at the bottom of the said flutes.
Presently, in medium and low-speed cigarette-making machines, it is sufficient to establish a mean value of the vacuum in order to guarantee correct braking of the cigarettes, both upon starting of the cigarette-making machine and upon maximum speed of production.
The above mentioned criterion of establishing a mean value of vacuum is not permissible in the high-speed cigarette-making machines. In fact, by this criterion, the braking effect is excessive when the machine is started, so that the cigarettes are braked in the flutes before reaching the abutment member at the end of the flute. On the other hand, the mean value of vacuum does not guarantee a sufficient braking effect at the highest production speeds, so that the cigarettes abut against the abutment members still at a high speed so that they may be damaged or bounce back, thus spoiling the correct formation of the row of consecutive cigarettes on the transfer drum.
In order to avoid the above mentioned inconveniences, the present invention proposes an automatic control device for suction braking the cigarettes as they enter at high speed the flutes of a transfer drum, which is characterized by the fact that it comprises an adjustable control device, usually in the form of a throttle valve, operatively inserted between the suction ports of the flutes and the vacuum source, said adjustable control device being capable of automatically adjusting the suction exerted by the flutes in a manner substantially proportional to the speed of production of the cigarette-making machine.
According to a first embodiment of the invention, the adjustable control device operates to control the rate at which vacuum is applied to the suction ports of the flutes.
According to another embodiment of the invention, the adjustable control device operates to selectively control, so as to open or close the channel vacuum, the number of suction ports connected to the source of vacuum.
The above and other features of the invention, and the advantages deriving therefrom, will appear evident from the following detailed description of some preferred embodiments, made by way of non-limiting examples.